The question of the intrinsic QCD uncertainties on the predicted particle spectra in DM annihilation is often neglected in the literature besides some comparisons between the predictions of different multi-purposes event generators such as Herwig and Pythia. For instance, a comprehensive analysis has shown that different MC event generators may have excellent agreement in both the peak as well as the bulk of the spectra while their agreement is not very good in the tails [1]}. Another study was done by the authors of the PPPC4DMID [2]} where they highlighted the differences between Herwig and Pythia event generators. The excellent level of agreement in the most-populated regions of particle spectra may be interpreted as due to the fact that the different MC generators tend to be tuned to roughly the same set of data mostly coming from LEP measurements at the \(Z\) -boson pole [3]}, [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, [10]}, [11]}, [12]}. Therefore, the envelope spanned by the predictions of the different MC models cannot represent the true estimate of the uncertainty on the predicted spectra.
